Wireless communication method and wireless communication device

ABSTRACT

Wireless communication methods and devices are provided. The wireless communication method includes transmitting a reference signal and a data signal in a Physical Resource Block (PRB) with a coverage enhancement level, wherein the number of resource elements transmitting the reference signal in the PRB is determined by the coverage enhancement level, the channel type and/or the coding rate of the data signal.

BACKGROUND 1. Technical Field

The present disclosure relates to the field of wireless communication,and in particular, to wireless communication methods and wirelesscommunication devices in Machine-Type Communication.

2. Description of the Related Art

MTC (Machine-Type Communication) is a new type of communication in 3GPP(The 3rd Generation Partnership Project) in release 12 and is animportant revenue stream for operators and has a huge potential from theoperator perspective. Based on the market and operators' requirements,one of the important requirements of MTC is improving the coverage ofMTC UEs (User Equipments). Thus, MTC will further be envisioned inrelease 13, for example, to support coverage enhancement of 15 dB. Thistype of coverage enhancement technique is quite useful for some MTC UEssuch as sensors in the basement which have large losses on their signalstrengths due to the penetration losses.

Repetition is one of key techniques to support MTC UEs in coverageenhancement. Specifically, for MTC UEs in coverage enhancement,basically each channel needs to do multiple repetitions (e.g., 100times). At the receiver side, the receiver combines all the repetitionsof the channel and decodes the information. Thus, coverage enhancementrequirement is reached by signal accumulation and power enhancementresulting from repetitions.

SUMMARY

One non-limiting and exemplary embodiment provides an approach tomaximally optimize the system performance in MTC with coverageenhancement.

In one general aspect, the techniques disclosed here feature a wirelesscommunication method, including: transmitting a reference signal and adata signal in a Physical Resource Block (FRB) with a coverageenhancement level, wherein the number of resource elements transmittingthe reference signal in the PRB is determined by the coverageenhancement level, the channel type and/or the coding rate of the datasignal.

It should be noted that general or specific embodiments may beimplemented as a system, a method, an integrated circuit, a computerprogram, a storage medium, or any selective combination thereof.

Additional benefits and advantages of the disclosed embodiments willbecome apparent from the specification and drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the specification and drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic diagrams each showing an example of BLERperformance of PUSCH repetitions;

FIG. 2 is a flowchart of a wireless communication method according to anembodiment of the present disclosure;

FIG. 3 is a flowchart of a wireless communication method according toanother embodiment of the present disclosure;

FIG. 4 is a block diagram showing a wireless communication deviceaccording to a further embodiment of the present disclosure; and

FIG. 5 is a block diagram showing a wireless communication deviceaccording to a still further embodiment of the present disclosure.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof. In the drawings,similar symbols typically identify similar components, unless contextdictates otherwise. It will be readily understood that the aspects ofthe present disclosure can be arranged, substituted, combined, anddesigned in a wide variety of different configurations, all of which areexplicitly contemplated and make part of this disclosure.

Underlying Knowledge Forming Basis of the Present Disclosure

In the repetition as one key technique of coverage enhancement for MTCas mentioned in the BACKGROUND, long repetitions will last a long timeand will ask MTC UEs to keep active for a long time to be always in areception state, which will largely consume UEs' power and occupy manysystem resources. Therefore, other coverage enhancement technique suchas RS (reference signal) density increase is a useful assistance torealize coverage enhancement to reduce repetition time.

In order to introduce the RS density increase simply, take one PRB(Physical Resource Block) as an example. One PRB consists of 14 symbolsin time domain and 12 subcarriers in frequency domain, and one symboland one subcarrier form one RE (Resource Element). That is to say, onePRB has 12×14 REs in total. It is specified in the standard that someREs are assigned for transmitting some kinds of reference signals andother REs are assigned for transmitting data signals in one PRB. For acertain reference signal in a normal usage case, the number of REsassigned for transmitting it in one PRB and positions thereof arespecified in the standard. Thus, the RS density, that is, the ratio ofREs for transmitting the reference signal to total REs in one PRB, isspecified in the standard. Accordingly, RS density increase meansincreasing the number of REs for transmitting the reference signal inone PRB.

By increasing the RS density, the channel estimation performance andthus signal quality can be improved, so that repetition times can bereduced for MTC UEs with coverage enhancement.

One straightforward solution to apply RS density increase is that allUEs and all channels assume the maximum RS density, for example 24 CRS(Cell-specific Reference Signal) REs and 24 DMRS (Demodulation ReferenceSignal) REs per PRB. However, based on our observations, some UEs cannotbenefit from RS density increase, but their performance will beimpacted. Also, some channels cannot benefit from RS density increasedue to impact on the coding rate. The detailed observations aredescribed below,

The first observation is based on PUSCH (Physical Uplink Shared Channel)simulation with varying repetition times and the number of subframescombined at the receiver side for demodulation. FIGS. 1A and 1B areschematic diagrams each showing an example of BLER (Block Error Rate)performance of PUSCH repetitions.

As shown in FIGS. 1A and 1B, FIG. 1A on the left and FIG. 1B on theright show simulation curves corresponding to two different repetitioncases respectively. In each of them, the horizontal axis represents theaverage SNR (Signal to Noise Ratio) and the vertical axis represents theaverage BLER. In the lower left corner of FIG. 1A and the lower rightcorner of FIG. 1B, simulation parameters are given specifically,Simulation parameters of FIG. 1A and FIG. 1B are same except thatrepetition time N_(Rep)=8 for FIG. 1A and repetition time N_(Rep)=128for FIG. 1B.

Further, as shown in the upper right corner of FIG. 1A and FIG. 1B, aparameter of N_(ave) represents the number of subframes combined in thereceiver side for joint channel estimation, Specifically, in FIG. 1A,for a case of 8 repetitions, the curve in dotted line corresponds to theideal channel estimation and three curves in solid lines correspond torealistic channel estimations when the number of subframes combined inthe receiver side to do joint channel estimation equals to 1, 4 and 8respectively. Similarly, in FIG. 1B, fora case of 128 repetitions, thecurve in dotted line corresponds to the ideal channel estimation andthree curves in solid lines correspond to realistic channel estimationswhen the number of subframes combined in the receiver side to do jointchannel estimation equals to 1, 4 and 8 respectively.

Intuitively, by comparing FIG. 1A and FIG. 1B, no matter whether theideal channel estimation or realistic channel estimations, the averageSNR of 8 repetitions is much larger than that of 128 repetitions forasame average BLER. Also, the performance gap between the ideal channelestimation curve and realistic channel estimation curves with 4 or 8subframes combining for the case of 8 repetitions in FIG. 1A is smallerthan that for the case of 128 repetitions in FIG. 1B. That is, theperformance gap between the ideal channel estimation curve and therealistic channel estimation curves becomes large as the number ofrepetitions increases.

In particular, when observing the average BLER=10⁻¹ as an example, bycomparing the ideal channel estimation curve with the curve for the caseof N_(ave)=8 as indicated by the bidirectional arrow, it can be easilyfound that the channel estimation gain is only about 1 dB for the caseof 8 repetitions as shown in FIG. 1A and reaches up to 6 to 7 dB for thecase of 128 repetitions as shown in FIG. 1B. That is to say, the channelestimation gain is quite limited in case of a small repetition time butlarge in case of a large repetition time.

It is noted that, although the simulation results come from the uplinksimulation, the above observation is also valid for downlink cases.Namely, the channel estimation performance improvement will largelyincrease BLER performance in lower SINR (Signal to Inference plus NoiseRatio) scenario (e.g., as shown in FIG. 1B) but only have a small effecton performance in relatively higher SINR scenario (e.g., as shown inFIG. 1A).

So from the above observation, it is meaningful to increase RS densityfor a large repetition time or long repetitions (a higher coverageenhancement level) which has relatively lower SINR as shown in FIG. 1B,instead of zero or a small repetition time or no or short repetitions(no or a lower coverage enhancement level) which has relatively higherSINR as shown in FIG. 1A.

The second observation is based on EPDCCH (Enhanced Physical DownlinkControl Channel) examples as follows.

As one example, assuming that EPDCCH is transmitted with one PRB whichhas 120 available REs, DCI (Downlink Control Information) size is 26bits with CRC (Cyclic Redundancy Check) and modulation is QPSK(Quadrature Phase Shift Keying), equivalent coding rate thereof isaround 26/(120×2)=0.108, which is quite low. In that case, in order toincrease RS density, some REs assigned for transmitting data signals areusually used for transmitting RS, which seems to have no big impact onthe coding rate. For example, using 12 data REs for transmitting RSadditionally will make the coding rate changed to 26/((120−12)×2)=0.120, which is still very low. And the change amount of the codingrate is 0.012, which is also very low,

As another example, assuming EPDCCH is transmitted with one ECCE(Enhanced Control Channel Element) which could carry 36 REs, DCI size isalso 26 bits with CRC and modulation is QPSK, equivalent coding ratethereof is 26/(36 ×2)=0.361, which is relatively high as compared withthe above example, In this case, replacing 3 or 6 data REs for RS REswill make the coding rate changed to 26/((36−3)×2)=0.394 or26/((36−6)×2)=0.433, which is also relatively high as compared with theabove example. And, the change amount of the coding rate is 0.033 or0.072, which is correspondingly high, Thus, replacing 3 or 6 data REsfor RS REs would have some impact on BLER performance. In that case, thechannel estimation gain resulting from the RS density increase may besmaller than a loss caused by the increased coding rate.

Therefore, from the above observation, it can be found that RS densityincrease is more reasonable in a case of a low coding rate (e.g., theformer example) than a case of a high coding rate (e.g., the latterexample), because it has almost no impact on the low coding rate but UE(User Equipment) can benefit from the channel estimation performanceimprovement resulting from the RS density increase.

It is noted that, although the results of the above observation arebased on downlink examples, the above observation is also valid foruplink cases.

Based on the above two observations, we need to consider in whichconditions the RS density increase is meaningful when adopting the RSdensity increase, so as to maximally optimize system performance.

In an embodiment of the present disclosure, there is provided a wirelesscommunication method 20 as shown in FIG. 2. FIG. 2 is a flowchart of awireless communication method according to an embodiment of the presentdisclosure. As shown in FIG. 2, the wireless communication method 20includes a step S201 of transmitting a reference signal and a datasignal in a PRB with a coverage enhancement level, In the wirelesscommunication method 20, the number of resource elements transmittingthe reference signal in the PRB is determined by the coverageenhancement level, the channel type and/or the coding rate of the datasignal.

Specifically, as described above, one FRB includes 12×14 REs in total,some of which are assigned for transmitting the reference signal (RS)and another some of which are used for transmitting the data signal. Forexample, the RS may be a DMRS which is used to demodulate thetransmitted signals containing the data in a UE (receiver side).However, the RS is not limited to a certain RS such as DMRS and may beall kinds of RSs. For example, when the wireless communication method 20is used in MTC, the RS may be a CRS.

Furthermore, for example, in MTC with coverage enhancement, a coverageenhancement level is defined to indicate the level or degree of coverageenhancement. The higher the coverage enhancement level is, the largerthe coverage enhancement is. In more particular, when employingrepetitions to implement coverage enhancement, the coverage enhancementlevel may also be represented by the repetition time. That is to say,the more the repetition time employed is, the larger the coverageenhancement is and thus the higher the coverage enhancement level is.

In addition, with respect to repetitions, it is well known that therepetition time may indicate the time the RS and the data signal aretransmitted repeatedly in subframes or in PRBs, One subframe consists oftwo slots, each of them contains 7 symbols in time domain, which is sameas one PRB. However, one FRB corresponds to 12 subcarriers in frequencydomain, and one subframe depends on the bandwidth in frequency domain.Thus, repetition in subframes means repetition in time domain only andrepetition in PRBs means repetition in both time domain and frequencydomain. It is noted that, although not exemplified here, repetition mayalso be implemented in frequency domain only.

Thus, according to an embodiment of the present disclosure, in thewireless communication 20, the coverage enhancement level may berepresented by the repetition time of transmission of the referencesignal and the data signal in time domain and/or in frequency domain,

Note that, the repetition as one of key techniques for coverageenhancement is only for illustration, the techniques for coverageenhancement are not limited to the repetition, and other techniques maybe used to implement coverage enhancement, When employing othertechniques, the coverage enhancement level may be represented by otherparameters instead of the repetition time.

Further, the wireless communication method 20 is suitable for MTC, butnot limited to MTC. It can be applied to any wireless communication withcoverage enhancement.

As described above, the number of REs transmitting the RS in the PRB maybe determined by the coverage enhancement level, the channel type and/orthe coding rate of the data signal. That is, one of or any combinationof the three parameters are used to implement RS density increase. Thedetails of the three parameters will be discussed later.

With the wireless communication 20, by increasing RS density based onthe coverage enhancement level, the channel type and/or the coding rateof the data signal, signal quality is improved and the power consumptionfor UEs with coverage enhancement is reduced.

According to an embodiment of the present disclosure, in the wirelesscommunication 20 as shown in FIG. 2, the number of resource elementstransmitting the reference signal in the PRB for a larger coverageenhancement level may be more than that for a smaller coverageenhancement level.

Specifically, as found in the first observation above, since thecommunication with a larger coverage enhancement level (e.g., a largerrepetition time) has relatively low SINR as shown in FIG. 1B and thechannel estimation performance improvement will largely increase itsBLER performance, it is meaningful to increase RS density in this case,that is, more RS REs in the FRB should be used for transmitting the RS.Meanwhile, the communication with a smaller coverage enhancement level(e.g., a smaller repetition time) has relatively higher SINR as shown inFIG. 1A and the channel estimation performance improvement only havesmall effect on its BLER performance, it is meaningless to increase RSdensity in this case, that is, less RS REs in the PRB should be used fortransmitting the RS.

In order for those skilled to understand more easily, PDSCH (PhysicalDownlink Shared Channel) is taken as an example. In the following, Table1 shows an exemplary usage of REs for transmitting the RS in the PRBbased on the coverage enhancement level.

TABLE 1 Coverage Enhancement Level 1 2 3 4 5 RS One or two Two or fourDMRS (two DMRS (two Maximum Configuration DMRS DMRS or four or four DMRSREs + ports: 12 ports: 24 ports, 24 ports, 24 maximum REs REs REs) +REs) + CRS REs + CRS (two CRS (four CSI-RS ports, 16 ports, 24 REs >48REs) = 40 REs) = 48 REs REs REs

In Table 1, the first line gives five different coverage enhancementlevels 1-5 and the second line shows RS configurations corresponding tothe coverage enhancement levels 1-5, respectively. Here, it is assumedthat the coverage enhancement level 1 indicates the smallest level(e.g., the smallest repetition times) and the coverage enhancement level5 indicates the largest level (e.g., the largest repetition times).

In a case of the smallest coverage enhancement level 1, the smallestnumber of REs in the PRB is used for transmitting the RS, that is, thesmallest RS density is employed since there is potentially no channelestimation gain resulting from RS density increase in this scenario asdiscussed previously. For example, as shown in Table 1, one or two DMRSports, i.e., 12 DMRS REs, may be used as RS REs here.

In a case of the coverage enhancement level 2 which is larger than thesmallest coverage enhancement level 1, the number of REs fortransmitting the RS in the PRB may be increased from the case of thesmallest coverage enhancement level 1. For example, as shown in Table 1,two or four DMRS ports, i.e., 24 DMRS REs, may be used as RS REs here.24 DMRS REs is the maximum DMRS RE configuration.

In a case of the coverage enhancement level 3 which is larger than thecoverage enhancement level 2, the number of REs for transmitting the RSin the FRB may be further increased from the case of the coverageenhancement level 2. For example, as shown in Table 1, in addition totwo or four DMRS ports, i.e., 24 DMRS REs, two CRS ports, i.e., 16 CRSREs, may be used as RS REs here. That is to say, there are 40 RS REs intotal in the PRB in this case.

In a case of the coverage enhancement level 4 which is larger than thecoverage enhancement level 3, the number of REs for transmitting the RSin the FRB may be further increased from the case of the coverageenhancement level 3. For example, as shown in Table 1, two or four DMRSports, i.e., 24 DMRS REs, as well as four CRS ports, i.e., 24 CRS REs,may be used as RS REs here, That is to say, there are 48 RS REs in totalin the PRB in this case. 24 CRS REs is the maximum CRS RE configuration.

In a case of the largest coverage enhancement level 5, the number of REsfor transmitting the RS in the PRB may be further increased from thecase of the coverage enhancement level 4. For example, as shown in Table1, in addition to the maximum DMRS RE configuration, i.e., 24 DMRS REs,as well as the maximum CRS RE configuration, i.e., 24 CRS REs, REsassigned for another RS such as CSI-RS (Channel State InformationReference Signal) may be used as RS REs here. That is to say, there aremore than 48 RS REs in total in the FRB in this case.

With the RS configuration based on the coverage enhancement level inTable 1, UE which cannot benefit from RS density increase will have noperformance loss.

It is noted that, the classification of coverage enhancement levels andcorresponding RS configurations in Table 1 are only for the purpose ofillustration, and the present disclosure is not limited thereto. Theclassification of coverage enhancement levels and corresponding RSconfigurations may be varied depending on specific practice.

Further, although determination of the number of RS REs in a PRB basedon the coverage enhancement level is explained specifically taking PDSCHas an example, the present disclosure is not limited thereto. Thepresent disclosure is also suitable for 15 PUSCH for example, and iseven applicable to any kinds of downlinks and uplinks.

By determining the number of RS REs in a PRB based on the coverageenhancement level, the wireless communication 20 can avoid increasing RSdensity unnecessarily and impacting original performance for UEs with asmaller coverage enhancement level due to increased overhead and codingrate.

According to an embodiment of the present disclosure, in the wirelesscommunication 20 as shown in FIG. 2, at least a part of the referencesignal transmitted in the PRB may reuse existing CRS, DMRS, CSI-RSand/or other existing reference signals.

Reusing these existing RSs means not only using REs assigned fortransmitting these existing RSs in the PRB but also using these signalsfor channel estimation, Specifically, RE configurations in a PRB forlegacy RSs such as CRS, DMRS, CSI-RS and the like are predefined in thestandard. These legacy RSs can be reused for increasing RS density.

For a MTC UE for example, depending on the specific requirement of RSdensity increase, the RS used for MTC may reuse existing CRS, DMRS,CSI-RS, that is, REs for transmitting the RS for MTC in the PRB maydirectly apply CRS REs, DMRS REs, CSI-RS REs and so on, For example, asshown in Table 1, for the coverage enhancement levels 1 and 2, DMRS isreused. When it is required to increase RS density for the coverageenhancement levels 3 and 4, CRS is additionally reused. When it isrequired to further increase RS density for the coverage enhancementlevel 5, DMRS, CRS and CSI-RS are all reused. In addition to REs oflegacy RS, signals of these legacy RSs may be directly used for the MTC.

By reusing legacy RSs for the RS in the wireless communication 20,existing RSs could be utilized as much as possible and increasing manyadditional RS REs is avoided, thus the resource utilization ratio isguaranteed.

According to an embodiment of the present disclosure, in the wirelesscommunication 20 as shown in FIG. 2, at least a part of the referencesignal transmitted in the PRB may be transmitted in resource elementsused for transmitting the data signal.

Specifically, when legacy RSs cannot be used for MTC for example, someREs assigned for transmitting the data signals can be used fortransmitting the RS. For example, it is assumed that only DMRS REs areavailable for PDSCH case in Table 1. Accordingly, in case of thecoverage enhancement level 3, in addition to the maximum DMRS REconfiguration, i.e., 24 DMRS REs, 16 REs assigned for transmitting datasignals may be used now for transmitting the RS instead of CRS REs. Thecases of the coverage enhancement levels 4 and 5 will be similar withthe case of the coverage enhancement level 3.

Therefore, based on the availability of legacy RSs and the number of RSREs to be increased, all of the RS may reuse legacy RSs, a part of theRS may reuse legacy RSs and the rest of the RS may be transmitted insome data REs in the PRB, or all of the RS may be transmitted in somedata REs in the PRB.

According to an embodiment of the present disclosure, in the wirelesscommunication as shown in FIG. 2, the number of resource elementstransmitting the reference signal in the PRB for a higher coding rate isless than that for a lower coding rate.

Specifically, as found in the second observation above, since there isalmost no impact on a low coding rate when increasing RS density, RSdensity increase is more reasonable in a case of a low coding rate thana case of a high coding rate. That is to say, more RS REs in the FRBshould be used for transmitting the RS in a case of a low coding rate,meanwhile less RS REs in the PRB should be used for transmitting the RSin a case of a high coding rate.

By determining the number of RS REs in a PRB based on the coding rate,the wireless communication 20 can avoid increasing RS densityunnecessarily and causing performance loss to UEs with a high codingrate.

According to an embodiment of the present disclosure, in the wirelesscommunication 20 as shown in FIG. 2, the data signal may be used fortransmitting PDSCH or PUSCH, and the usage of resource elements fortransmitting the reference signal in the FRB may be indicated by MCSindicated in DCI, which is transmitted in Physical Downlink ControlChannel (PDCCH) or EPDCCH.

Specifically, in order for those skilled to understand more easily,PDSCH is still taken as an example in which it is assumed that PDSCH istransmitted with one PRB with 120 available REs, and the modulation isQPSK. The usage (configuration) of RS in this case may be indicated inMCS which is indicated in DCI transmitted in PDCCH or EPDCCH. In thefollowing, Table 2 shows an example of RS density increase based on thecoding rate indicated by MCS (Modulation and Coding Scheme).

TABLE 2 Increased Modulation Number of RS MCS Index Order TBS IndexCoding Rate REs 0 2 0 0.067 24 REs 1 2 1 0.1 24 REs 2 2 2 0.134 24 REs 32 3 0.167 12 REs 4 2 4 0.233 12 REs 5 2 5 0.3 12 REs 6 2 6 N/A 0 7 2 70.433 0 8 2 8 0.5 0 9 2 9 0.567 0

In Table 2, the first column lists out MCS indices 0-9, and the secondcolumn gives the modulation order which equals to 2 for QPSK here.Further, the third column shows TBS (Transport Block Size) indices 0-9which correspond to MCS indices 0-9 of the first column one by one andrespectively indicates different sizes of data, i.e., different numbersof bits of data. Based on the number of bits indicated by each TBS indexas well as conditions assumed above, the corresponding coding rate ofeach TBS index may be calculated through the same computation method asthat in the second observation above. The fourth column gives thecalculated coding rates respectively corresponding to TBS indices 0-9.For example, TBS index 0 and MCS index 0 correspond to a coding rate of0.067, TBS index 1 and MCS index 1 correspond to a coding rate of 0.1,TBS index 2 and MCS index 2 correspond to a coding rate of 0.134, TBSindex 3 and MCS index 3 correspond to a coding rate of 0.167, TBS index4 and MCS index 4 correspond to a coding rate of 0.233, TBS index 5 andMCS index 5 correspond to a coding rate of 0.3, TBS index 6 and MCSindex 6 correspond to a coding rate of N/A, TBS index 7 and MCS index 7correspond to a coding rate of 0.433, TBS index 8 and MCS index 8correspond to a coding rate of 0.5, and TBS index 9 and MCS index 9correspond to a coding rate of 0.567.

Based on the above discussion, the number of RS REs in the PRB for ahigher coding rate should be less than that for a lower coding ratesince the RS density increase hardly impact the lower coding rate and UEcan benefit from the channel estimation improvement resulting from theRS density increase without suffering from increased coding rate.

In Table 2, the fifth column gives increased number of RS REs indifferent cases, Specifically, in cases of low coding rates of 0.067,0.1 and 0.134 respectively indicated by MCS index 0, 1 and 2, largest REdensity increase is employed, i.e., 24 REs are added for transmittingthe RS in the FRB. In cases of medium coding rates of 0.167, 0.233 and0.3 respectively indicated by MCS index 3, 4 and 5, medium RE densityincrease is employed, i.e., 12 REs are added for transmitting the RS inthe FRB. In cases of large coding rates of N/A, 0.433, 0.5 and 0.567respectively indicated by MCS index 6, 7, 8 and 9, RE density increaseis not employed, i.e., no RE is added for transmitting the RS in thePRB. Thus, the usage of REs for transmitting the RS (or the RS densityincrease) in the PRB can be indicated by MCS as shown in Table 2.

Note that, the increased number of RS REs (e.g., 24 or 12 REs) in Table2 is only for the purpose of illustration and the present disclosure isnot limited thereto. Further, although PDSCH is taken as an examplehere, the present disclosure is not limited thereto. The presentdisclosure is also suitable for PUSCH for example, and is evenapplicable to any kinds of downlink and uplink data.

In addition, as discussed before, the added 24 or 12 REs in this examplemay reuse legacy RSs, may be transmitted in some data REs in the PRB, ormay partially reuse legacy RSs and partially be transmitted in some dataREs in the PRB.

By indicating the usage of REs for transmitting the RS in the PRB byMCS, there is no need to set a new signaling to indicate the RS usage.

According to an embodiment of the present disclosure, in the wirelesscommunication 20 as shown in FIG. 2, the usage of resource elementstransmitting the reference signal in the PRB may be configured by RadioResource Control (RRC), may be predefined or may be recommended by auser equipment through Channel Quality Indicator (CQI).

Specifically, although an example that the usage of REs for transmittingthe RS in the PRB is indicated by MCS is given above, the presentdisclosure is not limited thereto. The detailed usage of increased RSREs may also be configured by RRC or predefined. Alternatively, UE mayalso recommend the RS density increase through CQI. Since RRC and CQIare existing signaling like MCS and configurations thereof are wellknown to those skilled in the art, no more details thereof will bediscussed here for avoiding redundancy. Similarly, there is no need toset a new signaling to indicate the RS usage in this case.

As mentioned previously, the number of REs transmitting the RS in thePRB may be determined by the channel type of the data signal. That is tosay, different channel may use different RS density.

According to an embodiment of the present disclosure, in the wirelesscommunication 20 as shown in FIG. 2, the data signal may be used fortransmitting PDCCH or EPDCCH, and the usage of resources elementstransmitting the reference signal in the PRB may be indicated by SIB(System Information Block) or may be specified.

Specifically, PDCCH and PDSCH are taken as an example. In general, it isassumed that PDCCH has a quite low coding rate, for example, uses onePRB to transmit DCI of 26 bits, but PDSCH uses a relatively high codingrate so as to guarantee the throughput. In this case, PDSCH usually usea normal RS density while PDCCH may use increased RS density. Thus, thechannel performance of PDSCH will not be impacted. Meanwhile, PDCCHalmost has no performance loss as well but can benefit from the channelestimation performance improvement resulting from the RS densityincrease.

In addition, the detailed usage of RS REs for PDCCH may be indicated bySIB. Alternatively, the detailed usage of RS REs for PDCCH may bespecified for example in specification. For example, for the purpose ofsimplicity, the maximum RS density (e.g., 24 CRS REs plus 24 DMRS REs)may be always assumed for PDCCH. In this way, there is no need to set anew signaling to indicate the detailed usage of RS REs for PDCCH.

Although PDCCH and PDSCH are taken as an example here, the presentdisclosure is not limited thereto and the above design is also suitablefor EPDCCH for example.

According to an embodiment of the present disclosure, in the wirelesscommunication 20 as shown in FIG. 2, the data signal may be used fortransmitting SIB1, and the usage of resource elements transmitting thereference signal in the PRB may be indicated by Master Information Block(MIB) or may be specified.

Specifically, SIBs are taken as an example. It is well known that UE hasno knowledge of the coverage enhancement level before or during SIBreception. In this case, it is impossible to determine the RS densityincrease for SIB1 based on the coverage enhancement level beforereception and demodulation of SIB1. Thus, when transmitting the SIB1 ina PRB, the usage of REs for transmitting the RS may be specified inspecification. For example, maximum RS density (e.g., 24 CRS REs plus 24DMRS REs) may be always assumed for SIB1.

Alternatively, the usage of REs for transmitting the RS for SIB1 mayalso be indicated in MIB. In this case, MIB is firstly demodulated atthe receiver side so that the usage of REs for transmitting the RS forSIB1 indicated in MIB can be obtained for demodulation of SIB1. Then,SIB1 is demodulated at the receiver side.

By indicating the usage of RS REs in the PRB for SIB1 by MIB orspecifying it, there is no need to set a new signaling to indicate thedetailed usage of RS REs for SIB1.

According to an embodiment of the present disclosure, in the wirelesscommunication 20 as shown in FIG. 2, the usages of resource elementstransmitting reference signals in PRBs for other SIBs are indicated bySIB1.

Specifically, since other SIBs are obtained after SIB1, the usages of RSREs in PRBs for other SIBs may be indicated by SIB1. In this way, afterSIB1 is received at the receiver side, the usages of RS REs in PRBs forother SIBs indicated by SIB1 can be obtained for decoding other SIBs.Then, other SIBs can be obtained at the receiver side.

By indicating usages of RS REs in PRBs for other SIBs by SIB1, moreflexibility of RS usage of SIBs is realized.

In another embodiment of the present disclosure, there is provided awireless communication method 30 as shown in FIG. 3. FIG. 3 is aflowchart of a wireless communication method according to anotherembodiment of the present disclosure. As shown in FIG. 3, the wirelesscommunication method 30 includes a step S301 of receiving a referencesignal and a data signal in a PRB transmitted with a coverageenhancement level. In the wireless communication method 30, the numberof resource elements transmitting the reference signal in the PRB isdetermined by the coverage enhancement level, the channel type and/orthe coding rate of the data signal.

With the wireless communication 30, by increasing RS density based onthe coverage enhancement level, the channel type and/or the coding rateof the data signal, signal quality is improved and the power consumptionfor UEs with coverage enhancement is reduced.

According to an embodiment of the present disclosure, in the wirelesscommunication 30 as shown in FIG. 3, the number of resource elementstransmitting the reference signal in the PRB for a larger coverageenhancement level is more than that for a smaller coverage enhancementlevel.

According to an embodiment of the present disclosure, in the wirelesscommunication 30 as shown in FIG. 3, the number of resource elementstransmitting the reference signal in the FRB for a higher coding rate isless than that for a lower coding rate.

Note that, the other technical features in the above wirelesscommunication method 20 can also be incorporated in the wirelesscommunication device 30.

In a further embodiment of the present disclosure, there is provided awireless communication device 40 as shown in FIG. 4. FIG. 4 is a blockdiagram showing the wireless communication device 40 according to afurther embodiment of the present disclosure.

As shown in FIG. 4, the wireless communication device 40 includes atransmission unit 401 configured to transmit a reference signal and adata signal in a PRB with a coverage enhancement level. The number ofresource elements transmitting the reference signal in the PRB isdetermined by the coverage enhancement level, the channel type and/orthe coding rate of the data signal.

The wireless communication device 40 according to the present embodimentmay further include a CPU (Central Processing Unit) 410 for executingrelated programs to process various data and control operations ofrespective units in the wireless communication device 40, a ROM (ReadOnly Memory) 430 for storing various programs required for performingvarious process and control by the CPU 410, a RAM (Random Access Memory)450 for storing intermediate data temporarily produced in the procedureof process and control by the CPU 410, and/or a storage unit 470 forstoring various programs, data and so on. The above transmission unit401, CPU 410, ROM 430, RAM 450 and/or storage unit 470 etc. may beinterconnected via data and/or command bus 490 and transfer signalsbetween one another.

Respective units as described above do not limit the scope of thepresent disclosure. According to one embodiment of the disclosure, thefunction of the above transmission unit 401 may also be implemented byfunctional software in combination with the above CPU 410, ROM 430, RAM450 and/or storage unit 470 etc.

With the wireless communication device 40, by increasing RS densitybased on the coverage enhancement level, the channel type and/or thecoding rate of the data signal, signal quality is improved and the powerconsumption for UEs with coverage enhancement is reduced.

In a still further embodiment of the present disclosure, there isprovided a wireless communication device 50 as shown in FIG. 5. FIG. 5is a block diagram showing the wireless communication device 50according to a still further embodiment of the present disclosure.

As shown in FIG. 5, the wireless communication device 50 includes areception unit 501 configured to receive a reference signal and a datasignal in a PRB transmitted with a coverage enhancement level. Thenumber of resource elements transmitting the reference signal in the PRBis determined by the coverage enhancement level, the channel type and/orthe coding rate of the data signal.

The wireless communication device 50 according to the present embodimentmay further include a CPU 510 for executing related programs to processvarious data and control operations of respective units in the wirelesscommunication device 50, a ROM 513 for storing various programs requiredfor performing various process and control by the CPU 510, a RAM 515 forstoring intermediate data temporarily produced in the procedure ofprocess and control by the CPU 510, and/or a storage unit 517 forstoring various programs, data and so on. The above reception unit 501,CPU 510, ROM 513, RAM 515 and/or storage unit 517 etc. may beinterconnected via data and/or command bus 520 and transfer signalsbetween one another.

Respective units as described above do not limit the scope of thepresent disclosure. According to one embodiment of the disclosure, thefunction of the above reception unit 501 may also be implemented byfunctional software in combination with the above CPU 510, ROM 513, RAM515 and/or storage unit 517 etc.

With the wireless communication device 50, by increasing RS densitybased on the coverage enhancement level, the channel type and/or thecoding rate of the data signal, signal quality is improved and the powerconsumption for UEs with coverage enhancement is reduced.

Note that, the wireless communication device 40 and the wirelesscommunication device 50 can be an eNB (eNodeB), a UE or the likedepending on specific application scenarios. Further, the technicalfeatures in the above wireless communication methods 20 and 30 can alsobe incorporated in the above wireless communication devices 40 and 50respectively.

The present disclosure can be realized by software, hardware, orsoftware in cooperation with hardware. Each functional block used in thedescription of each embodiment described above can be realized by an LSIas an integrated circuit, and each process described in the eachembodiment may be controlled by LSI. They may be individually formed aschips, or one chip may be formed so as to include a part or all of thefunctional blocks. They may include a data input and output coupledthereto. The LSI here may be referred to as an IC, a system LSI, a superLSI, or an ultra LSI depending on a difference in the degree ofintegration. However, the technique of implementing an integratedcircuit is not limited to the LSI and may be realized by using adedicated circuit or a general-purpose processor. In addition, an FPGA(Field Programmable Gate Array) that can be programmed after themanufacture of the LSI or a reconfigurable processor in which theconnections and the settings of circuits cells disposed inside the LSIcan be reconfigured may be used.

It is noted that the present disclosure intends to be variously changedor modified by those skilled in the art based on the descriptionpresented in the specification and known technologies without departingfrom the content and the scope of the present disclosure, and suchchanges and applications fall within the scope that claimed to beprotected. Furthermore, in a range not departing from the content of thedisclosure, the constituent elements of the above-described embodimentsmay be arbitrarily combined.

Embodiments of the present disclosure can at least provide the followingsubject matters.

(1). A wireless communication method comprising:

transmitting a reference signal and a data signal in a Physical ResourceBlock (PRB) with a coverage enhancement level, wherein

the number of resource elements transmitting the reference signal in thePRB is determined by the coverage enhancement level, the channel typeand/or the coding rate of the data signal.

(2). The method according to (1), wherein the number of resourceelements transmitting the reference signal in the PRB for a largercoverage enhancement level is more than that for a smaller coverageenhancement level.

(3). The method according to (1), wherein at least a part of thereference signal transmitted in the PRB reuses existing Cell-specificReference Signal (CRS), Demodulation Reference Signal (DMRS), ChannelState Information Reference Signal (CSI-RS) and/or other existingreference signals.

(4). The method according to (1), wherein at least a part of thereference signal transmitted in the PRB is transmitted in resourceelements used for transmitting the data signal.

(5). The method according to (1), wherein the number of resourceelements transmitting the reference signal in the PRB for a highercoding rate is less than that for a lower coding rate.

(6). The method according to (1), wherein the data signal is used fortransmitting Physical Downlink Shared Channel (PDSCH) or Physical UplinkShared Channel (PUSCH), and the usage of resource elements fortransmitting the reference signal in the PRB is indicated by Modulationand Coding Scheme (MCS) indicated in Downlink Control Information (DCI),which is transmitted in Physical Downlink Control Channel (PDCCH) orEnhanced Physical Downlink Control Channel (EPDCCH).

(7). The method according to (1), wherein the usage of resource elementstransmitting the reference signal in the PRB is configured by RadioResource Control (RRC), is predefined or is recommended by userequipment through Channel Quality Indicator (CQI).

(8). The method according to (1), wherein the data signal is used fortransmitting PDCCH or EPDCCH, and the usage of resources elementstransmitting the reference signal in the PRB is indicated by SystemInformation Block (SIB) or is specified.

(9). The method according to (1), wherein the data signal is used fortransmitting SIB1, and the usage of resource elements transmitting thereference signal in the PRB is indicated by Master Information Block(MIB) or is specified.

(10). The method according to (1), wherein the usages of resourceelements transmitting reference signals in PRBs for other SIBs areindicated by SIB1.

(11). A wireless communication method comprising:

receiving a reference signal and a data signal in a Physical ResourceBlock (PRB) transmitted with a coverage enhancement level, wherein

the number of resource elements transmitting the reference signal in thePRB is determined by the coverage enhancement level, the channel typeand/or the coding rate of the data signal.

(12). The method according to (11), wherein the number of resourceelements transmitting the reference signal in the PRB for a largercoverage enhancement level is more than that for a smaller coverageenhancement level.

(13). The method according to (11), wherein the number of resourceelements transmitting the reference signal in the PRB for a highercoding rate is less than that for a lower coding rate.

(14). A wireless communication device comprising:

a transmission unit configured to transmit a reference signal and a datasignal in a Physical Resource Block (PRB) with a coverage enhancementlevel, wherein

the number of resource elements transmitting the reference signal n thePRB is determined by the coverage enhancement level, the channel typeand/or the coding rate of the data signal.

(15). A wireless communication device comprising:

a reception unit configured to receive a reference signal and a datasignal in a Physical Resource Block (PRB) transmitted with a coverageenhancement level, wherein

the number of resource elements transmitting the reference signal in thePRB is determined by the coverage enhancement level, the channel typeand/or the coding rate of the data signal.

(16). The method according to (1), wherein the coverage enhancementlevel is represented by the repetition time of transmission of thereference signal and the data signal in time domain and/or in frequencydomain.

It is noted that the technical features in the above wirelesscommunication methods can also be incorporated in the above wirelesscommunication devices. In addition, embodiments of the presentdisclosure can also provide an integrated circuit which comprisesmodule(s) for performing the step(s) in the above respective wirelesscommunication methods. Further, embodiments of the present can alsoprovide a computer readable storage medium having stored thereon acomputer program containing a program code which, when executed on acomputing device, performs the step(s) of the above respective wirelesscommunication methods.

What is claimed is:
 1. A wireless communication method comprising:transmitting a reference signal and a data signal in a Physical ResourceBlock (FRB) with a coverage enhancement level, wherein the number ofresource elements transmitting the reference signal in the PRB isdetermined by the coverage enhancement level, the channel type and/orthe coding rate of the data signal.
 2. The method according to claim 1,wherein the number of resource elements transmitting the referencesignal in the PRB for a larger coverage enhancement level is more thanthat for a smaller coverage enhancement level.
 3. The method accordingto claim 1, wherein at least a part of the reference signal transmittedin the PRB reuses existing Cell-specific Reference Signal (CRS),Demodulation Reference Signal (DMRS), Channel State InformationReference Signal (CSI-RS) and/or other existing reference signals. 4.The method according to claim 1, wherein at least a part of thereference signal transmitted in the PRB is transmitted in resourceelements used for transmitting the data signal.
 5. The method accordingto claim 1, wherein the number of resource elements transmitting thereference signal in the PRB for a higher coding rate is less than thatfor a lower coding rate.
 6. The method according to claim 1, wherein thedata signal is used for transmitting Physical Downlink Shared Channel(PDSCH) or Physical Uplink Shared Channel (PUSCH), and the usage ofresource elements for transmitting the reference signal in the PRB isindicated by Modulation and Coding Scheme (MCS) indicated in DownlinkControl Information (DCI), which is transmitted in Physical DownlinkControl Channel (PDCCH) or Enhanced Physical Downlink Control Channel(EPDCCH).
 7. The method according to claim 1, wherein the usage ofresource elements transmitting the reference signal in the PRB isconfigured by Radio Resource Control (RRC), is predefined or isrecommended by user equipment through Channel Quality Indicator (CQI).8. The method according to claim 1, wherein the data signal is used fortransmitting PDCCH or EPDCCH, and the usage of resources elementstransmitting the reference signal in the PRB is indicated by SystemInformation Block (SIB) or is specified.
 9. The method according toclaim 1, wherein the data signal is used for transmitting SIB1, and theusage of resource elements transmitting the reference signal in the FRBis indicated by Master Information Block (MIB) or is specified.
 10. Themethod according to claim 9, wherein the usages of resource elementstransmitting reference signals in PRBs for other SIBs are indicated bySIB1.
 11. A wireless communication method comprising: receiving areference signal and a data signal in a Physical Resource Block (PRB)transmitted with a coverage enhancement level, wherein the number ofresource elements transmitting the reference signal in the PRB isdetermined by the coverage enhancement level, the channel type and/orthe coding rate of the data signal.
 12. The method according to claim11, wherein the number of resource elements transmitting the referencesignal in the PRB for a larger coverage enhancement level is more thanthat for a smaller coverage enhancement level.
 13. The method accordingto claim 11, wherein the number of resource elements transmitting thereference signal in the PRB for a higher coding rate is less than thatfor a lower coding rate.
 14. A wireless communication device comprising:a transmitter that transmits a reference signal and a data signal in aPhysical Resource Block (PRB) with a coverage enhancement level, whereinthe number of resource elements transmitting the reference signal in thePRB is determined by the coverage enhancement level, the channel typeand/or the coding rate of the data signal.
 15. A wireless communicationdevice comprising: a receiver that receives a reference signal and adata signal in a Physical Resource Block (PRB) transmitted with acoverage enhancement level, wherein the number of resource elementstransmitting the reference signal in the PRB is determined by thecoverage enhancement level, the channel type and/or the coding rate ofthe data signal.